Describing individual variation in local sweating during exercise in a temperate environment.

Area of Science:

• Exercise Physiology
• Human Physiology
• Thermoregulation

Background:

• Individual variation in whole-body sweat rate (WBSR) is linked to heat balance.
• Previous research suggests heat balance status influences sweat rate variability.

Purpose of the Study:

• To investigate if local sweat rate (LSR) on the forehead and forearm can be predicted by a whole-body heat balance approach.
• To determine the relationship between LSR(head), LSR(arm), and the ratio of evaporative heat loss required for balance to maximum possible evaporation (E (req):E (max)).

Main Methods:

• Twelve males cycled at 60% VO2max in controlled environmental conditions.
• Measured rectal, aural, and mean skin temperatures, metabolic expenditure, and work rate.
• Estimated WBSR(ss), LSR(head), and LSR(arm) using body mass changes and absorbent patches.

Main Results:

• WBSR(ss) strongly correlated with E (req):E (max) (r=0.87, P<0.001).
• LSR(head) correlated with E (req):E (max) (r=0.82, P=0.001), and LSR(arm) correlated with both E (req) (r=0.62, P=0.031) and E (req):E (max) (r=0.78, P=0.003).
• Both LSR(head) and LSR(arm) showed significant correlations with WBSR(ss).

Conclusions:

• Individual variation in WBSR(ss), LSR(head), and LSR(arm) is effectively described by the E (req):E (max) ratio.
• The findings support using a whole-body heat balance approach to understand local sweat rate variations.